In silico optimization of charge separating dyes for solar energy conversion

Abstract

Dye-Sensitized Photoelectrochemical Cells are promising devices in solar energy conversion. However, several limitations still have to be addressed, such as the major loss pathway through charge recombination at the dye-semiconductor interface. Charge separating dyes constructed as push-pull systems can increase the spatial separation of electron and hole, decreasing the recombination rate. Here, we in silico investigate a family of dyes, consisting of polyphenylamine donors, fluorene bridges and perylene monoimide acceptors using a combination of semi-empirical nuclear dynamics and a quantum propagation of photoexcited electron and hole. To optimize the charge separation, several molecular design strategies are investigated, including modifying the donor molecule, increasing the π-bridge length and decoupling the molecular components through steric effects. It is found that the combination of a triphenylamine donor, using an extended 2-fluorene π-bridge and decoupling the different components by steric hindrance from side groups results in a dye with significantly improved charge separation properties in comparison to the original supramolecular complex.